1. Technical Field
The invention relates generally to radio frequency identification, and more particularly, to a method, system, and program product for automatically attenuating RFID antennas and recovering from failure or an RFID antenna or reader.
2. Background Art
Radio frequency identification (RFID) is a widely-used method for identifying and/or tracking items. RFID may be used, for example, to maintain an inventory of goods or to grant access to secured areas by an individual carrying an RFID device.
Generally, employing RFID in the performance of such tasks requires the establishment of an RFID network, including RFID readers, in order to read RFID “tags” within the network. RFID readers emit radio waves capable of detection by RFID tags. An RFID tag is essentially a bundled microchip and antenna capable of detecting the radio waves emitted by an RFID reader and returning to the reader information stored on the microchip. Typically, an RFID tag includes a unique serial number, allowing for unique identification of the tag and, consequently, an item bearing the tag.
Establishing an RFID network can be time consuming and expensive. Generally, RFID readers must be extensively calibrated in order to function well within a chosen area. Such calibration may be complicated, for example, by the presence of interfering devices, building materials, etc. Typically, the calibration of RFID readers requires a radio frequency (RF) specialist to investigate the environment in which the network will be employed and decide on an appropriate network configuration. Such configuration includes, for example, the ranges and operating channels of individual readers and their antennas. The actual establishment of the RFID network may include further calibration to accommodate site-specific variables.
Common problems with RFID networks include reader collision and tag collision. Reader collision is caused by the overlap of the radio waves of different RFID readers. RFID tags are unable to simultaneously respond to signals from multiple RFID readers and consequently may not respond to signals from any RFID reader. Tag collision involves the presence of a large number of RFID tags in a relatively small area, such that too many tags attempt to simultaneously respond to an individual RFID reader. Avoiding these and other problems involves the proper placement and calibration of RFID readers throughout the area to be covered by the RFID network.
For example, referring to FIG. 1, an RFID network 100 is shown, comprising a plurality of RFID readers 120, 122, 124, 126 within an network area 110. As shown, the RFID readers include omnidirectional antennas, such that their coverage areas 130, 132, 134, 136 are substantially circular. Antennas producing other signal patterns are also commonly employed. Ideally, RFID readers are deployed such that an RFID tag 140, 142 anywhere within network area 110 will receive a signal from only one RFID reader. In FIG. 1, however, this is not the case. RFID tag 140 is not within the coverage area of any RFID reader and, as a consequence, is “invisible” to network 100. In addition, RFID tag 142 is within the range of two RFID readers 120, 126, as it is located within an overlap zone 150. As such, RFID tag 142 may be subject to reader collision and unable to respond to either RFID reader. Other overlap zones 152, 154 are shown between coverage areas 130 and 134 and coverage areas 132 and 134, respectively.
An additional problem of network 100 is that a large portion 160 of network area 110 is not serviced by the coverage area of any RFID reader. This may be particularly problematic in cases where an RFID tag is affixed to a movable object. Such an RFID tag will appear to move into and out of network 100 as the tag moves from into and out of the coverage areas of RFID readers.
One solution to the problems shown in FIG. 1 is to change the location of one or more RFID reader within network area 110. For example, FIG. 2 shows network 100 following the relocation of RFID readers 120, 122, and 126. As can be seen, RFID tag 140 is now within coverage area 130 of RFID reader 120 and RFID tag 142 is within coverage area 136 of RFID reader 126 only. Such a solution is not ideal, however. A large portion 160 of network area 110 is still not covered by the coverage area of any RFID reader. In addition, the movement of either or both RFID tags 140, 142 may require again relocating one or more RFID reader.
Maintenance of an RFID network is similarly labor-intensive. The failure of an RFID reader or antenna within an RFID network is likely to leave at least a portion of the network's coverage area unserviced. For example, referring now to FIG. 3, the network 100 of FIG. 2 is shown, wherein RFID reader 126 has, for any number of reasons, become inactive. As a result, RFID tag 142 is no longer within the coverage area of any RFID reader. As in FIG. 2, one or more RFID readers could be relocated such that their coverage areas include the portion of network area 110 previously covered by RFID reader 126. As explained above, such an approach is both time-consuming and expensive. In deployments where the loss of signal from an RFID reader is a frequent occurrence, such an approach becomes impracticable.
In addition, once an RFID network is established and calibrated, its components generally must be replaced with the same or similar components, which often must be recalibrated in order to function within the network. The addition of an RFID reader to an existing network can be more complicated, as doing so often requires the recalibration of readers adjacent the new reader in order to reduce interference caused by the new reader.
To this extent, a need exists for a robust RFID network that does not require relocation of RFID readers following the failure of an RFID reader or antenna or the addition of an RFID reader to the RFID network.